A new service called webRTC, i.e. real time communication services like a voice and video calls, is specified in IETF (Internet Engineering Task Force) and it is taking up momentum. WebRTC interworks with other networks so that is not operating as a standalone silo service. This means for the end customer that you do not want to call only other webRTC users, but also normal phones.
In order to provide this functionality, studies in 3GPP (3rd Generation Partnership Project) is being carried as disclosed by NPL 1.